China Spallation Neutron Source (CSNS) has started to serve the users since March of 2018. To upgrade the beam power to 500 kW and improve the performance of ion source, an RF coupled H$^-$ source is under development. The source has a Si$_3$N$_4$ ceramic plasma chamber surrounded by a 4.5-turn antenna. The plasma is ignited by a pulsed DC spark gap and then driven by a 2 MHz solid-state amplifier with a repetition rate of 25 Hz. The commissioning of the source started in the January of 2019. When un-cesiated, it produced more than 30 mA beam at an RF power of 32 kW and pulse width of 450 $\mu$s. Further improvements are still ongoing.
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